Ultrastructure and cell division of an oral bacterium resembling Alysiella filiformis

Abstract

Alysiella filiformis is commonly found on the epithelial cells of the oral cavity in rabbits. An ultra-structural study of these cells has shown A. filiformis attached by numerous slime appendages (setae) to the host epithelial cells. The organism possesses a multilayered cell wall 18–22 nm thick. Cell division occurs by constriction of the cytoplasm with concurrent septum formation initiating from the dense innermost layer of the cell wall. This is followed by thickening and delamination of the septum with subsequent invagination of the outer layers of the cell wall causing a partial cell separation. However, the cells of the typical trichomes are still held together by septal bridges. Mesosome-like structures were occasionally found and were often in the area of septum formation. All attempts to culture this organism in vitro were unsuccessful.